Air breathing flask for foundry molds

ABSTRACT

DISCLOSED HEREIN IS A FLASK AND POURING APPARATUS FOR CASTING MOLTEN METALS USING VAPORIZABLE PATTERNS WHEREIN THE FLASK HAS AIR BREATHING WALLS THAT ARE PROVIDED WITH A PERMEABLE LAYER, SLOTTED VENTS, OR SCREEN VENTS.

,March 23, 1971 C. a MEZE'Y ET A? 3,572,421

AIR BREATHING FLASK FOR FOUNDRY MOLDS Filed Dec. 11, 196'?l INVENTORS.

CHARLES C. MEZEY ANGELO PAOLI WHEELER WHEELER HOUSE 81 CLEMENCY Attorn eys United States Patent Oice 3,572,421 Patented Mar. 23, 1971 U.S. Cl. 164-237 6 Claims ABSTRACT F THE DISCLOSURE Disclosed herein is a flask and pouring apparatus for casting molten metals using vaporizable patterns wherein the ask has air :breathing walls that are provided with a permeable layer, slotted vents, or screen vents.

BACKGROUND OF THE INVENTION When using vaporizable patterns such as disclosed in Shroyer Pat. No. 2,830,343, a pattern is embedded in a mold forming material and is vaporized by the heat of the molten casting charge as the charge is poured into the mold. The gases created on vaporization of the pattern by the heat of the molten casting charge must be dispersed through the mold forming material in order to clear the cavity left by the vaporization of the pattern. The gases that penetrate the mold forming material are often prevented from escaping to the atmosphere due to the presence of the solid walls of the flask. In any type casting this can become quite serious since a large amount of gases are created on vaporization of the pattern which must be vented to the atmosphere to allow for the rapid and :steady flow of molten material into the mold. The gases, if prevented from escaping rapidly to the atmosphere, may retard the flow of molten material into the cavity in the mold as well as adversely effecting the surface finish of the casting.

SUMMARY OF THE INVENTION The present invention overcomes the above disadvantages by providing a flask for casting molten metals which allows the gases created on vaporization of a cellular plastic pattern to escape rapidly to the atmosphere. The walls of the ask are provided with a number of openings or perforations to vent the gases to the atmosphere. The openings or perforations are covered with a permeable layer or are closed by gas permeable inserts to prevent the mold forming material from flowing out of the ask through the openings. The layer may be made from asbestos or other similar material which is gas permeable. The gas permeable inserts are made with -slots or are covered with a permeable screen to obstruct the flow of mold forming material from the mold while allowing the gases in the mold to escape to the atmosphere. In either instance the gases created on vaporization of the pattern will be free to liow through the mold forming material and out through the perforations in the walls of the flask, without disturbing the molding medium.

Other objects and advantages will become apparent from the following detailed description when read in connection with the following drawings in which:

FIG. 1 is a side view in section of a mold showing a vaporizable pattern embedded within the mold forming material.

FIG. 2 is an enlarged view in section of a perforated side wall of the mold of FIG. 1.

FIG. 3 is an enlarged view of a section of a modified type wall for a mold.

FIG. y4 is a view of another modified wall for a mold having inserts in the perforations in the side wall.

FIG. 4a is a view of the wall for a mold having a modified insert positioned in the perforations.

FIG. 5 is a front view of one of the inserts for the wall of FIG. 4.

FIG. `6 is a front view of another insert for the Wall of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, a mold 10 is shown with a ask or container 12. A pattern 16 is embedded within a mold forming material 20 in the ask with a sprue 22 (see FIG. l) connected to the pattern 16 and extending upward to the open end of the ilask. The sprue is lined with a cardboard or paperboard sleeve 23. A polystyrene or ceramic sleeve may also be used with this casting arrangement.

A combination pouring basin and mold weight 24 made from cast iron or steel is placed on the top or open end of the ask with the opening 25 of the basin located above the sprue 22. This is the general arrangement of the mold prior to pouring a molten casting charge into the pouring basin 24. The Weight of the pouring basin must `be sufficient to hold the mold forming material within the flask during the pouring operation.

The pattern 16 is made of a cellular plastic material, i.e. polystyrene or polyurethane, which has been cut or molded to the .shape of the article to be cast. This pattern material is vaporizable substantially without residue upon subjection to the heat of molten casting charge. A coating of refractory material 26 is applied to the outer surface of the pattern and must be gas permeable and must remain solid at the temperature of the molten casting charge to allow the gases created upon vaporization of the pattern to escape into the mold forming material.

The mold forming material 20 includes a conventional molding sand, having a binder, or can be of a loose freeilowing material such as dry, unbonded sand. The pouring basin-mold weight 24 is placed on the top of the mold forming material in the flask with the opening 25 in the mold forming material on the bottom of the basin aligned with the paperboard tube or sleeve 23 in the sprue 22 in the mold forming material. When the molten casting charge is poured into the pouring basin-mold Weight, it will flow through the cardboard ysleeve 23 and will contact the pattern. The heat of the molten casting charge will vaporize the pattern 16. The gases created on vaporization of the pattern will pass through the coating of refractory material and will be diffused into the mold forming material. These gases must be allowed to escape rapidly to the atmosphere or they will adversely alect the casting formed in the cavity left by the vaporized pattern.

In FIG. 1 the Walls 12 and bottom 14 of the container or flask are shown with a number of perforations 30 which are used to vent the gases to the atmosphere. The mold forming material will have a tendency to liow through these perforations 30 unless some gas permeable means is used to prevent the mold forming material from owing out of the flask. To prevent this a gas permeable layer 32 is used to cover the perforations 30. The layer 32 may be secured to the outside of the liask or mold wall, FIG. 2, or the layer 32 may be placed within the walls 12a and 12b, as seen in FIG. 3. In the embodiment shown in FIG. 3, the layer 32 is built into the wall 12a and 12b in a sandwich arrangement.

The layer 32 may be formed from an asbestos cloth, stainless steel screen or any line mesh material that is gas permeable and capable of withstanding the temperature of the gases at the walls of the flask. Gases escaping through the mold forming material will flow through the perforations 301 in the wall of the flask and bottom board out to the atmosphere through the layer 32. The layer 32 is particularly important if a loose free-flowing material such as unbonded sand is used for the mold forming material since this material will have a greater tendency to ow out through the perforations 30.

In FIG. 4 a modied wall arrangement for the flask 12 is shown having perforations 40` which are larger than perforations 30. This type of a wall is used where large castings are being made and large amounts of gases are created on vaporization of the pattern. The perforations 40 are closed by gas permeable means such as the slotted plugs or inserts 42 or the screened plug or inserts 42, FIG. 4a. All of the perforations 40` may be filled with one or the other of the plugs or inserts. In FIG. 5 the front 46 0f the slotted inserts 42 is shown with a number of parallel slots 48 that pass through the front of the plug. In FIG. 6 the center of the plug is shown filled with a line mesh wire screen 50 that will allow gases to flow out of the ask and at the same time prevent any loss of the mold forming material.

When the mold 10 is being prepared for use, an initial amount of mold forming material 20, such as unbonded sand is poured into the iiask and the pattern 16, which has a refractory coating 26, is placed in position. More of the mold forming material is poured into the flask to substantially completely cover the pattern and is rammed or vibrated so that the sand settles rmly about the pattern. 'Ihe cardboard or paperboard sleeve 23 for sprue 22 is placed in communication with the pattern in the ask and the ask completely lilled with the mold forming material.

The combination pouring basin and mold weight 24 is placed on the top or open end of the ask with the grooves or serrations 52 firmly embedded in the mold forming material to prevent any movement or shifting of the pouring basin during the cast operation. Opening 25 in the pouring basin should be aligned with the sprue 22, as seen in FIG. l. When the molten casting charge is poured into the pouring basin, it will liow through the cardboard or paperboard sleeve lining the sprue 22 into contact with the pattern. The heat of the molten charge will vaporize the pattern and the molten charge will lill the space left by the vaporized pattern. The gases created on vaporization will be ditiused into the mold forming material and will flow out through perforations 30` and layer 32 to the atmosphere.

Although only a few embodiments of the present invention have been shown and described, it should be apparent that various changes and modifications can be made herein without departing from the scope of the appended claims.

What we claim is:

1. A casting arrangement comprising the combination of,

a container having an open top and a plurality of perforations formed in the sides thereof,

a quantity of a mold forming material in a relatively owable state disposed within said container and comprised of dry loose unbonded particles,

a plastic pattern having the shape of an article to be cast, said pattern being embedded in said dry loose unbonded particles and being vaporizable by the heat of a molten casting charge,

gas permeable closure means comprising a layer of gas permeable material covering said perforations on the outside of the container for preventing the ow of the relatively flowable dry mold forming material out through said perforations while allowing for the free flow of gases therethrough, and

a heavy pouring member having a pouring aperture through which said molten casting charge is to be poured into the mold, said pouring member being disposed on and substantially closing the top of said container and having a plurality of projections extending into said dry owable mold forming material said member being of sufficient weight to prevent displacement of the owable material within the container during the pouring operation.

2. The casting arrangement according to claim 1 wherein said gas permeable closure means comprises a layer formed of a gas permeable material.

3. The combination of,

a flask having side walls and a bottom wall, a plurality of perforations formed in said side walls and bottom Wall,

gas permeable layer means on the outside of the ask and covering said perforations,

a relatively owable mold forming material disposed in said flask and comprising dry loose unbonded particles,

a plastic pattern embedded in said mold forming material and being vaporizable on subjection to a molten casting charge,

a tubular sprue connected to said pattern and embedded in said mold forming material, and

a heavy pouring member havng a pouring aperture through which said molden casting charge is to be poured into said mold, said pouring member being disposed on and substantially closing the top of said container and having a plurality of projections extending into said dry owable mold forming material, said member being of suicient weight to prevent displacement ofthe liowable material within the container during the pouring operation.

4. The combination according to claim 3 wherein said gas permeable closure means comprises a layer formed of a permeable material.

5. The combination according to claim 3 wherein said sprue is lined with a paperboard sleeve.

6. The combination according to claim 3 wherein said heavy pouring member has a serrated bottom constituting the projections which are embedded in said mold forming material to prevent its displacement.

References Cited UNITED STATES PATENTS `3,222,738 12/ 1965 Carter 164-34 3,189,958 6/1965 Newbold 164-410X 3,157,924 11/1964 .Smith 164-34 644,425 2/1900 Harrison 164--410X 1,369,182 2/1921 Moore 164-376 2,243,445 5/ 1941 Summy 164-376 3,443,627 5/ 1969 Watts 164-244X 3,098,268 7/1963 Ziiferer 164-16 2,060,350 11/1936 Siler 164-410 3,259,677 7/1966 Zwick 249-141X 3,429,360 2/ 1969 Olson 164-3 83X FOREIGN PATENTS 789,769 1/ 1958 Great Britain.

I. SPENCER OVERHOLSER, Primary Examiner V. K. RISING, Assistant Examiner U.S. C1. X.R. 

